Give a toddler an iPhone and 10 minutes, and she’ll take at least 50 selfies and buy a car on eBay. Give her an iPad, and she’ll stumble upon decidedly non-kid-friendly episodes of Breaking Bad.

With smartphones and tablets, children are exposed to an unprecedented amount of screen time on a daily basis. As with other tech toys, kids can pose a hazard to smart devices, possibly cracking the screen or dropping it a cereal bowl in the process. But how will exposure to these screens affect their brains and behavior?

Most of the research on screen time has focused on television. Previous studies suggest that children under 30 months learn less from educational TV programs like Sesame Street than they do from real-life interactions. TV exposure can take the place of playing outside and chatting and playing with parents and other caregivers — with negative effects on the child’s development. Too much TV has been linked to issues with language development, attention issues and, perhaps less directly, obesity. And in older children, the amount of time a child spends watching TV also corresponds to the degree of change seen in their growing brains.

But there aren’t many published studies on toddlers and tablets, so for the most part it’s an open question what effect adding a smartphone and iPad to the 60-inch LED TV will have on a developing child. “As parents we will need to keep adapting to a changing culture and rapidly evolving technologies, and it’s our job to protect our child’s most important relationships and learning experiences while not driving ourselves crazy with guilt for every bit of screen time our child gets,” says Jenny Radesky, a pediatrician at Boston University Medical Center.

Radesky and her Boston University colleagues Jayna Schumacher and Barry Zuckerman published a review paper on the subject in the January 1 Pediatrics. They call for new recommendations for parents and more research on the effects of this particular flavor of screen time on toddlers. Based on what little work has been done, they also offer some preliminary guidance.

The TV studies can provide guidelines about how long kids should be watching and at what age. In 1999, the American Academy of Pediatrics came out with a statement discouraging media use in children under two years old. They reaffirmed that position in 2011, and again in October of 2013. However, the organization has yet to take a direct stance on smartphones and tablets.

While these devices can function as simple viewing screens, smartphones and tablets can be more than a portable television. For one thing, they’re interactive. That opens the door to potential education and development benefits. “No app can read a child’s cues and respond contingently the way a caregiver can, at least not yet,” Radesky says. “But apps can respond to child prompts, taps or vocalizations.” This interactive facet might mean children could learn from small screen media at an earlier age than current recommendations suggest.

Dimitri Christakis, a pediatrician at Seattle Children’s Research Institute, advocated as much in an opinion piece in JAMA Pediatrics last May. But, linking screen time to what’s going on in the brain and to behavior is hard. His lab recently found that 15- to 18-month-old toddlers playing with blocks had higher levels of cortisol, a hormone that regulates stress levels, compared with those watching DVDs. That would suggest that a little stress, measured by cortisol in this experiment, may be associated with activities that toddlers can learn from. Christakis thinks that, when it comes to cortisol levels, tinkering with apps on a tablet may be more like playing with blocks than watching a screen. But researchers don’t really know what healthy levels of cortisol are in infants. In general, it’s also hard to link cortisol levels to long-term brain or behavior effects.

Tablets and smartphones can also facilitate interactions with parents, family and friends. A 2013 study in Child Development found that video chatting through a smartphone app can be just as effective as chatting in person when it comes to helping 24- to 30-month-old children bond and learn new words.

Last year, Laura Sanders wrote about her involvement in a project at Georgetown University that’s looking further into how children interact with video calls. Radesky is keen to investigate what kids can learn from apps versus the real world and whether apps might be more beneficial for some children versus others — like kids who develop language skills slower or those with neurobiological issues.

In the education realm, there’s a lot of potential, but also a lot of hype. E-books and apps designed to help kids learn to read could help with early literacy by exposing toddlers to letters, words and phonetics. The few studies that have been done focus on older children, though.

At the same time, e-books often come with extras like sound effects and videos that can be distracting, potentially messing with the child’s attention and understanding of the story or the task or the lesson they’re supposed to be learning. “The delight a child gets from touching a screen and making something happen is both edifying and potentially addictive,” Christakis writes. Just like with TV, setting limits reduces the potential for developing tablet-addicted toddlers. At this point, Radesky and her colleagues affirm that it’s up to parents to use their best judgment. Trying an app or game before turning a toddler loose on it is always a good idea, they write.

It’s hard to sift through the millions of apps out there that market themselves as education products to figure out what actually works and what doesn’t. For now, parents looking for advice on the subject can turn to organizations that focus on early childhood development, like Zero to Three or Resources for Early Learning. The New America Foundation has reviewed some literacy apps, but their effectiveness may depend on the level of stimulation and the child’s age. “For kids 2 and younger, there’s no evidence that apps can teach anything,” Radesky says.

Despite the call for more research on the subject, results from ongoing and future studies may not even end up vindicating or condemning toddlers’ exposure to tablets and smartphones. “It’s not a pro or con, black or white type of argument,” says Radesky. “It’s more about balance, content and how we use the device.”

And while the long-term effects of small-screen screen time on toddlers remain unclear, anecdotal field studies and tech repair shops confirm that toddlers can be lethal to smartphones and tablets.